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- Durability and shrinkage of concrete with CDW as recycled aggregates: Benefits from superplasticizer’s incorporation and influence of CDW compositionPublication . Bravo, Miguel; De Brito, Jorge; Evangelista, Luis; Pacheco, JoãoThe shrinkage and durability properties of a total of 34 concrete mixes with recycled aggregates produced from different untreated construction and demolition waste (CDW) were tested. The effect of a polycarboxylic superplasticizer on the enhancement of these properties is presented, discussed, and compared with the findings of studies on concrete whose recycled aggregates are sourced from concrete. All properties were significantly affected by recycled aggregate incorporation and this effect was strongly dependent on the properties of the recycled aggregates of each specific source. The superplasticizer was less efficient in mixes with CDW than when the recycled aggregates were produced from concrete, the most common source of recycled aggregates in experimental works, despite untreated CDW being more practical and desirable from an industrial and environmental perspective.
- Performance of mortars with commercially-available reactive magnesium oxide as alternative binderPublication . Bravo, Miguel; Forero, Javier A.; Nobre, José; De Brito, Jorge; Evangelista, LuisThis paper intends to analyze the performance of mortars with reactive MgO, as a sustainable alternative to cement. Six different MgOs from Australia, Canada, and Spain were used in the production of mortars as partial substitutes for cement, namely 5%, 10%, 15%, 20%, and 25% (by weight). MgOs with different levels of reactivity were used to analyze its influence on the performance of MgO mortars. In order to evaluate the mechanical performance of these mortars, compressive strength, flexural strength, dynamic modulus of elasticity, and ultrasonic pulse velocity tests were performed. Compressive strength tests showed that the use of 25% reactive MgO can cause a decrease of this property of between 28% and 49%. The use of reactive MgO affected the other mechanical properties less. This paper also intends to analyze the durability performance of mortars with reactive MgO. To that effect, water absorption by capillarity was assessed. In this research, the effect of using MgO on the shrinkage was also analyzed. It was found that shrinkage may decrease by more than a half in some cases.